Burning Hunk2.

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I have a double door Bullard stove in my basement. These don't seem to be as well known as Fisher or Timberline, but are of the same basic old school heavy duty construction. The existing baffle/smoke shelf is hollow, and has a blower attachment that blows air from the back of the stove through the baffle and out the sides into the room, something the other manufacturers did not do. I have the original owners manual if anyone would like a copy. After reading a lot on secondary air retrofits, I decided to try a home project to install secondaries in the ol' girl. The pictures will help explain the text below.

Part 1: Materials and Construction

First off, I have to thank my friend Woody, who performed most of the welding and fabrication on this project. I supplied the materials and design (and Labatt Blue), he supplied his wire-feed welder, grinders, and skill. It turned out to be a pretty good after-work project.

I used 1 1/2" square tube steel to form and weld the box beams on each side of the firebox; it's in a "C" shape if you were to look at the stove from the left side. Each end of the box beam has a cap welded on it. A 7/8" hole was drilled in each side of the stove and into the box beams near the bottom front of the firebox with a slider type mechanism on on the outside to control the amount of secondary air allowed into the boxbeam and the tubes. Holes were also drilled on the inside wall of the top box beam for secondary air tubing connection. The draft will pull the secondary combustion air through the exteriror hole into the front of the box beam, move it horizontally to the back of the stove, then vertically up the back wall, and then horizontally again where it enters the stainless tubes and spills out into the firebox. The surface of the box beam is exposed to the fire/coals/ash in the firebox for the entire length, superheating the secondary air before it exits through the tubing. The entrance hole at the bottom of the flow path does not allow smoke to come out when the doors are open for loading, as the smoke will not travel "downhill" through a path of greater resistance.

4 pieces of 3/4" stainless steel pipe was used for the secondary air tubes, the holes were sized and angled in accordance with the Englander 30-NC secondary air tube architecture (you can find this info on their website). These were tack welded onto the box beam on each side. They seem to fit tight enough in the box beam's drilled holes to prevent much air leakage around them. The holes were drilled 1/16" larger than the tubing.

I purchased a baffle board for a Quadrafire 5700 and a piece of ceramic blanket from the local Quadrafire dealer, and fit them above the tubes. I reinstalled the existing firebrick, added some additional firebrick on the upper sides and upper back of the firebox for insulation to maintain the required box temps for secondary air ignition, and hooked the chimney connector back up.

Part 2: Firing

I started up the stove with the secondary air sliders closed and the door spinners (primary air) open. I burned down the first load of smaller starting wood and then put 6 splits on the coals, established a good fire with these, and let the stove surface temperature get up to about 550 degrees. There was a good amount of smoke coming out the chimney at this time. I then opened the secondary air sliders, fully shut the door spinners, then opened each door spinner 1 turn (this doesn't allow much air into the stove). I checked the secondary draft opening with a lit match, it sucked the match flame right out (apparently good draft was established)!

After 1 minute (or less), I looked at the chimney, NO VISIBLE SMOKE. I guess it works! The stove top climbed to over 700 deg, then settled back down to 650 deg. Two hours later, the stove top was still a solid 650 degrees, still no smoke. Six hours later the stove top temp had dropped somewhat, to just below 400, but there was still a pretty good amount of fuel left in the firebox. This scenario would not have played out like this prior to the retrofit.

The only thing is, as with most of these older units, it has solid cast doors and I cannot see what is happening, only via indicators from the chimney and the stove temp. I thought about making a new door opening and putting a big Blaze King glass door on it, but then I would have to come up with an all-new primary air inlet system. And air wash for the glass. Maybe next year...

Much thanks to this forum for all the topics and thoughts on secondary air, without it I probably wouldn't have attempted to build such a device. I'm very happy with the results and also with this superb site.

Minister of Fire2.

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TX-L, congrats, VERY well done retro-fit. I really like the way you routed the air intake. You put some thought into this, it shows. Agree with you on the cast door/ glass re-fit. It presents some obstacles. I didn't re-fit mine due to legit concerns about cracking the castings due to stressors from removing material for the glass. You can build new plate steel ones and use a similar primary air inlet, just get used to cleaning the glass. Once again, nicely done.

Member2.

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Great post. What diameter holes did you drill in the stainless and what was the hole spacing?

What it takes to keep me warm.... not necessarily happy
Blaze King KTJ 302
Cottonwood, Chinese Elm, scrap lumber, once in a while GOOD wood.... but not too often
Stihl Super 029 16 inch bar
Suzuki Sidekick
home made log splitter with 13 hp Honda
once in a while, someone stupid enough to go out with me to get wood.....

Mooderator2.

NULL

Staff Member

Nice job. That should make quite a difference. I like that you are letting the secondary air get preheated. One thing that seems a bit overkill is the number of secondary holes. The total area of the holes looks like it far exceeds the area of the intakes.

With your friend's welding skills, you should be able to make up some door windows, but at present there is no air wash, so I am not sure how well they will stay clean. Ceramic for the doors can be found at www.onedayglass.com. They will custom cut for you and are affordable.

PE Alderlea T6 - the gentle giant and a Jotul 602, the little stove that could“Sometimes I wonder whether the world is being run by smart people who are putting us on, or by imbeciles who really mean it.” - Mark Twain -
"A poor worker always blames his tools." - Dad

Burning Hunk2.

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The holes in the secondary tubes were taken from an Englander NC 30 stove manual, as the firebox size for this model and mine are about the same. This can be found on page 16 in the following document: http://www.englanderstoves.com/manuals/30-NC.pdf

I considered that the amount of holes may be more volume than the inlets for secondary air, but went with the Englander pattern anyway due to the same firebox volume (not necessarily the same dimensions). I mulled this over for a while, and didn't come to any definite conclusions.

This modification has changed the operation of this stove, and definitely for the better. I have started drawing a preheated primary air intake mmodification for an air wash on the glass, and think I will start this project next spring sometime. The only problem is that I will have to get the beast out of the basement and up to my buddy's garage for this next phase. I'm getting sick of lugging on it; once was enough!

I have a single door Timberline just sitting in my parents barn, in very good shape, that I think I'll do the same thing with and put it in the hunting camp next year.

New Member2.

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TX-L: I've been thinking along the same lines as you with respect to adding secondary combustion tubes. For me, they would go into a wood furnace, which has a thin metal box lined with a single upright row of firebricks along the bottom. I'm concerned that if I installed secondary combustion tubes high above these bricks, I'd be introducing too much heat high in the combustion chamber, where the metal is quite thin. Any notions about this? Are you still content with your retrofit?

Minister of Fire2.

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Well done! Gotta get you some glass so you can see the flame show. This is the same pattern / layout I used for my retrofit - seems to work well, though I'm a bit baffled as to the orientation of the tubes - mainly #3. My thought is that each tube should emit a flame which would hit the tube in front of it, adding extra heat to each tube as the flame flows to the front. They were very specific tube 3 should have a 275º angle, but it seems to hit the baffle in my case...may have to tweak it one of these days.

Re: Hole diameter - while it's true the number of holes have much greater area than the intake, IMHO, this is largely irrelevant. The goal isn't really to provide a 1:1 ratio - otherwise you could just run a 7/8" pipe right from the side of the stove to the secondary burn area. The main goal is to bring the air in, provide a relatively large 'chamber' for the air to heat, then move it slowly to allow extra heating and finally let it flow through a diffuse number of holes.

A 'cone' of flame develops around each hole where the hot air and smoke interact to make flame at the 'surface' but the inner 'core' is mainly just air. So you have to figure ~80 small cones of flame from all those holes mixes the air better and has more 'burning' surface area than a few larger cones which would form around larger holes.

Minister of Fire2.

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With your friend's welding skills, you should be able to make up some door windows, but at present there is no air wash, so I am not sure how well they will stay clean​

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Just a thought,
My Elm has no air wash and it stays crystal clear. Its done with 2 panes of glass. Basically insulating the window like your double pane in your house and therefore keeping the glass hot enough to stayed burned clean.. Not sure if the outer pane would need to be ceramic. Ocassionally on reload if I do something stupid I can get smoky glass but as soon as its up to temp it burned clean again. Seen stoves with airwash and the galss is still dirty but also seen some that work encredibly well.

Burning Hunk2.

NULL

I'm concerned that if I installed secondary combustion tubes high above these bricks, I'd be introducing too much heat high in the combustion chamber, where the metal is quite thin. Any notions about this? Are you still content with your retrofit?

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Farmer, you may (you should anyway to promote firebox temps for secondary combustion) have to install an insulated baffle right above the tubes to protect adjacent thin metal, but the heat is going to go somewhere... it will protect direct flame contact on the thinner metal though. I am very content with the retrofit; see below. Oh, and I have an older Massey 165!

fire it up man, we must see how it actually works!

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Motor7, It works! When I reload seasoned hardwood on a hot established bed of coals, the stovetop will cruise at about 850. It does this almost every time I use it, so it isn't a fluke one-time event. I know that seems like overfire, but the primary air is shut down almost completely and the stack key damper is shut. The secondaries ABSOLUTELY work (I just can't see 'em)! The 850 temp doesn't concern me, those old stoves were built extremely well with heavy, thick steel. Seems like the stack temp 2' above the collar is around 400 or so, but I don't specifically remember. This stove is installed in the garage and isn't used a whole lot. Straight chimney of about 16 -18 feet high.

Corey, agree with everything and good insight on your part. I don't know why the Englander burn tube angles are different from one to the next; my Liberty angles all look the same for each burn tube. At any rate, I tried to match up the retrofit with the Englander specs.

wkpoor, I wouldn't hesitate to try the glass without an airwash, I just don't want to risk ruining the doors by trying to cut holes in them. I would rather get an existing glass door and build/weld on the stove to fit the new door. However, a replacement door is fairly costly for just a stove that is randomly used to heat the garage. Example: $250 for a Lopi Liberty replacement door at the local dealer. And it's very hard to find only a used stove door, they usually have the rest of the stove attached. I have two friends who have Quads, I think they have air wash, their glass is often white -- it looks like a layer of ash on the inside of the glass.

Minister of Fire2.

NULL

Motor7, It works! When I reload seasoned hardwood on a hot established bed of coals, the stovetop will cruise at about 850. It does this almost every time I use it, so it isn't a fluke one-time event. I know that seems like overfire, but the primary air is shut down almost completely and the stack key damper is shut​

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Those results mirror what I see. With my primary full shut(really full shut) and key damper full closed I go right to 800-900. Only difference is I can look at the show. I will say running an EPA configuration blind would seem a bit odd. You would be relying on top temps vs air setting alone to know its working. Another thing to note is when reloading if the interior is white you know it was a nice clean hot burn.

New Member2.

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I am new, and this thread is kindly old but still interesting, by the way my name is Kees Ijpelaar and I live in holland.

I do experiment sometimes with my old stove, a french one.

I have look at the manual page 16 of the 30-NC about the distance of the holes and diameter, it is not clear how to see that. only the inches I can read
and use. but the .1875 and .1625 I can not.

I have a stove and want to try this, winter is coming so I can go start.

Can you also say how thick the tubes are, is this inside or outside measurement.

I did drawn some what I mean, I use 5 x 5 cm tubing with one 4 mm hole, not two because
I have no place, except when I do staple two tubes in length of the stove with holes on both sides, and there the bricks up.

Preheat tube rvs 5 x 5 cm wide, for the new idea I need another one on top of that or use only one inlet and one tube,
this one the hot, red glowing when look in it from the ouside hole.

Pictures are from the present changes, I do want to go now for the tubes aproach because it looks good.

metal whool in the preheat tube can give a mucho more heat exchange earea for who it make concern.